ATLANTA -- In one of the first studies of its kind, researchers at the University of California San Francisco report that an herbal compound significantly reduced prostate specific antigen (PSA) levels, an indicator of cancer cells, in men with advanced prostate cancer.
In response to the herbal compound, seventy-five percent of the men in the UCSF study experienced more than a 50 percent decline in their PSA levels. Men in the study include those who had never received hormonal therapy before (hormone-naïve) and patients with hormone-resistant prostate cancer, whose tumors no longer responded to hormonal therapies.
The compound, called PC-SPES ("PC" stands for prostate cancer, "SPES" is Latin for hope) is a combination of eight Chinese herbs, the most common of which is saw palmetto. It is commercially available at health food stores as an over-the-counter supplement for the treatment of prostate cancer.
During the UCSF study, a total of 61 men (27 with hormone-naïve prostate cancer, and 34 with hormone-resistant prostate cancer) were clinically evaluated for preliminary results. Study participants received nine capsules daily of PC-SPES. The majority of these men are still enrolled in the clinical trial and continuing treatment at this time.
"Our findings suggest that PC-SPES may have efficacy as a treatment for some men with prostate cancer," said Eric Small, MD, UCSF assistant clinical professor of medicine, co-author of the study. "However, as of yet, we cannot precisely pinpoint the estrogenic or active anti-cancer ingredients, if any, that PC-SPES may contain."
Small reports that 27 (100 percent) of the hormone-naïve patients experienced more than a 50 percent decline in their PSA levels.
Likewise, 19 out of 34 (58 percent) hormone-resistant patients also demonstrated more than a 50 percent decline in their PSA levels.
He notes that the study's results are preliminary and require further evaluation and a longer follow-up period (minimum of two years). Although not all of the study participants were eligible for evaluation at this time, a total of seventy men have enrolled in the study and begun treatment with PC-SPES.
In addition, Small reports that shrinkage of some of the men's prostate cancer tumors was observed. Some of the side effects of the compound included impotency, lowered sex drive and breast tenderness--all common conditions associated with hormonal therapies. However, overall, the therapy was well tolerated.
According to Small, PC-SPES may work in part like a hormonal therapy for prostate cancer because it demonstrated an anti-testosterone effect in hormone-naïve prostate cancer patients by mimicking the female hormone, estrogen. The compound may contain other active anti-cancer ingredients because it also lowered PSA levels in men in the study whose tumors have become resistant to hormonal treatments.
In their initial stages of growth, prostate cancer cells require androgens, or the male hormone called testosterone, to survive. Hormone therapy is a method of reducing or eliminating a man's supply of testosterone to a prostate tumor. One method of achieving this is by giving a man the female hormone, estrogen, which counters the effects of testosterone and shuts down the gland in a man's brain that stimulates the testicles to produce hormones.
However, although prostate cancer cells require androgens to survive initially, tumors can become independent of these hormones. When this occurs, tumors develop the ability to grow and spread regardless of the circulating hormones in the body. This stage of disease is called androgen-independent or hormone-resistant prostate cancer.
"As our study continues, we ultimately hope to learn a number of things about PC-SPES," Small says. "For instance, we aim to determine what percentage of men with hormone-naïve and hormone-resistant prostate cancer have declines in their PSA levels with use of the herbal compound; how long the anti-cancer and PSA-lowering effects of PC-SPES lasts; what the short and long-term effects of the therapy are; and how declines in PSA correlate with other measures of anti-cancer activity such as changes in tumor imaging and scanning."
Other authors on the paper include Robert Bok, MD, clinical instructor of medicine; Michele Corry, UCSF RNP; Mark Frohlich, MD, UCSF clinical instructor of medicine; Hiroko Kameda, UCSF research assistant; W.K. Kelly, MD, urologist oncologist at Memorial Sloan-Kettering Cancer Center; and David Reese, MD, UCSF assistant clinical professor of medicine. The PC SPES study is supported by the Association for the Cure of Cancer of the Prostate (CaP CURE).